This started as one problem and moved on to being another...

This problem started two Saturdays ago after doing some pretty aggressive riding. I was running fairly steady around 10,000rpms, when all of a sudden my bike felt jerky, like it was jumping up and down 100 rpms or so. I wasn't sure if I was imagining it or not. I rode on the freeway for a few days after, and as I held the throttle steady it had the same feeling. But looking at the gauges the tachometer and speedometer held steady.

I hit the twisties again last Wednesday and kept the bike around 9500rpms. I glanced at my gauges at one point and saw the tachometer drop 500rpms, with me holding the throttle steady, and the bike slowing. So now I know it wasn't me imagining it. That was the biggest jump, but mostly it felts like it was always about to run out of gas.

Another symptom is that the throttle would occasionally lag. Rolling all the way off to slow down, then applying the throttle again to speed up creates a delay as I roll back on the throttle. It'd do nothing, then jerk me a little.

And I'm not sure if this is relevant, but whenever I slow from 9k rpms or above, it backfired all the way down to 7k rpms. Or at least it popped, which I think is backfiring?

I checked the spark plugs to see if maybe they were bad, or showed signs of running lean or rich but they all look good. Then I dove into the carbs, cleaning and adjusting them. Everything looked clean and normal. The float guages are at the right height, the diaphragms don't have any holes, and the pilot jets are where they should be.
I started it up yesterday after doing all that adjusting. Before adjusting the carbs it would jump 50rpms constantly while at idle. Every other second it'd move up then down 50.
Now it seems to still be doing that, but it'll also randomly pick up and drop a couple hundred rpms. If I leave it on and don't touch anything, about every 15 seconds it will go up around 2000 rpms, wait 15 seconds then drop to 1500, wait 15 seconds then drop to 1200, wait 15 seconds then rise to 1500, etc.
Revving it got it up to redline, and it felt steady, but it felt steady back when the problem first started and it was actually jumping 100rpms extremely quickly.

Today I took apart the spark plug wires so see if they were rusted or anything, but they all look fine. Started the bike again with the choke on it wandered around a couple thousand rpms. Then I turned the choke off and it idled around 1000 rpms, and messing with the idle adjustment screw didn't seem to have any effect. When I tried to give it gas it stalled out.

And I killed the battery trying to start it again. It's been taking a beating for the past 3 days and I never charged it. So I'm done working on it today.

Basically, it ran fine for 8,000 miles since I've owned it (bike has 29k), then all of a sudden it started acting up.

Any ideas? Because I have no freaking clue.